Abstract
In our previous study, temporin-GHaR (GHaR) showed potent antimicrobial activity with strong hemolytic toxicity. To overcome its weakness, we designed GHaR6R, GHaR7R, GHaR8R, GHaR9R, and GHaR9W by changing the number of positive charges and the hydrophobic surface of GHaR. With the exception of GHaR7R, the hemolytic toxicity of the derived peptides had been reduced, and the antimicrobial activities remained close to the parent peptide (except for GHaR9R). GHaR6R, GHaR7R, GHaR8R, and GHaR9W exhibited a great bactericidal effect on Streptococcus mutans (S. mutans), which is one of the main pathogens causing dental caries. According to the membrane permeation and scanning electron microscope (SEM) analysis, these derived peptides targeted to the cell membranes of planktonic bacteria, contributing to the disruption of the membrane integrity and leakage of the intracellular contents. Moreover, they inhibited the formation of biofilms and eradicated the mature biofilms of S. mutans. Compared with GHaR7R, the derived peptides showed less cytotoxicity to human oral epithelial cells (HOECs). The derived peptides are expected to be the molecular templates for designing antibacterial agents to prevent dental caries.
Highlights
Dental caries is considered to be the most common oral disease and related to a variety of bacteria, of which Streptococcus mutans (S. mutans) is a significant contributor to tooth decay [1,2]
The increase of an appropriate number of positively charged amino acid residues on Antimicrobial peptides (AMPs) can enhance their antibacterial activity, and effectively reducing the hydrophobicity decrease the hemolytic toxicity of AMPs [17,18]
GHaR9W was obtained by displacing leucine with tryptophan, which is the important residue of AMPs contributing to the destructive effect on the bacterial membrane [19]
Summary
Dental caries is considered to be the most common oral disease and related to a variety of bacteria, of which Streptococcus mutans (S. mutans) is a significant contributor to tooth decay [1,2]. S. mutans produces many extracellular polysaccharides (EPS), which promotes the adhesion of bacteria on the surface of teeth and the co-aggregation with other microorganisms. Biofilms are highly organized microbial communities, in which the extracellular matrix provides a physical barrier for the bacteria and protect them from the antibiotics and environmental stress factors [4,5]. There are two commonly used methods of eradicating oral biofilms, including mechanical removal and drug dissolution [7]. They have been successfully used, the disadvantages still need to be overcome. Mechanical methods to remove dental plaque, such as brushing and flossing, are difficult to Molecules 2020, 25, 5724; doi:10.3390/molecules25235724 www.mdpi.com/journal/molecules
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